Knowledge Center | Koch Agronomic Services
Knowledge Center | Koch Agronomic Services
Maximizing Top-Dress Applications
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There is resurgence in interest on topdressing nitrogen for a variety of reasons. First, the perception is that top-dressing nitrogen fertilizer during the growing season offers potential benefits in cost and efficiency. Second, recent weather patterns have forced many farmers to either skip or miss the opportunity for fertilizer application prior to or at seeding time. Finally, protein premiums for spring wheat can be enticing at times

The less than ideal spring conditions (i.e., cool, dry or extremely wet) have made many farmers understandably cautious about their fertilizer application rates. However, environmental conditions can change very quickly, and crop prospects can improve almost overnight. Crops can significantly benefit from additional nitrogen if this suitable situation arises.

With a few precautionary measures and timely precipitation, top-dressed nitrogen can effectively boost yields and produce attractive economic benefits. Research over the years has shown that under ideal conditions, top-dressed nitrogen can produce yield responses that are very similar to nitrogen banded at seeding.

To make top-dressed nitrogen effective, it is important to recognize the factors that influence performance and improve effectiveness:

Application Timing

  • To have an impact on yield, the sooner the nitrogen gets into the plant, the better.
  • Yield responses to N can be obtained when applied 2-3 weeks following crop emergence.
  • As a rule, apply prior to tillering in cereals and bolting in canola. If application is delayed, the impact of the nitrogen will shift from yield to protein enhancement. In that case, hard red spring wheat is a good candidate for top-dressing.

Importance of Rainfall

 Timely rainfall is the most important factor. Top-dressed nitrogen, regardless of the nitrogen product used, will only become effective once it is moved into the rooting zone. Either irrigation or a significant rainfall event of more than 1/2” is required. Monitor weather patterns and apply supplemental nitrogen, if precipitation is expected within 2-3 days.

Product Selection and Application Method

Several nitrogen products can be used for topdressing. All perform well if there is significant precipitation within hours of application.The longer the exposure on the soil surface, the greater the difference in product performance.The difference in performance is primarily due to volatilization losses that occur with surface applied urea or both volatilization and denitrification losses for urea plus nitrate containing products, such as UAN.  

How can Volatilization and Denitrification Losses be Minimized? 

The use of a urea stabilizer and nitrification inhibitors with proven effectiveness, such as AGROTAIN®, AGROTAIN® PLUS SC, CENTURO® and TRIBUNE® can help combat these losses. Research has shown that volatilization losses can be as significant as 40% but using AGROTAIN treated urea can help decrease of volatilization losses protecting a grower’s nitrogen investment. Using AGROTAIN PLUS SC can not only protect against ammonia volatilization but denitrification and leaching losses as well. We are looking forward to the results from our research with TRIBUNE that started in the three prairie provinces this year.

To learn more about a solution for your top-dress applications contact your KAS representative today. 

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Nitrogen loss can be a serious problem impacting yield potential and return on investment. Depending on the soil type, nitrogen fertilizer is susceptible to losing more than 50% of its nitrogen through ammonia volatilization, denitrification and nitrate leaching.
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